1. Field of the Invention
Embodiments of the present invention relate to work supports. More particularly, embodiments of the present invention relate to double acting fluid advanced work supports with sequenced clamping and unclamping processes.
2. Description of the Related Art
Work supports typically utilize a pressurized medium, such as hydraulic fluid, to diametrically activate a clamping mechanism which holds a plunger in a fixed position in order to provide support for a work piece while the work piece is being processed in an assembly or manufacturing environment. Double acting work supports also use the pressurized fluid to extend the plunger to the work piece and retract the plunger from the work piece. Often, the same flowable medium pathway or circuit is utilized to extend and clamp the plunger as well as retract and unclamp the plunger. Since the plunger is being extended toward the work piece at the same time as the pressurized fluid is contracting the clamping mechanism, it is possible that the clamping mechanism may clamp the plunger in a fixed position before the plunger has extended to the work piece. As a result, the work piece may not have proper support while it is being processed.
Work supports also often include a piston and a spring within the plunger to assist the plunger in extending to the work piece before the clamping mechanism is fully contracted and locks the plunger in a fixed position. Usually, the spring and the piston are positioned such that pressurized fluid will fully advance the piston while compressing the spring to control contact force when the plunger contacts the work piece. When it is time to retract and unclamp the work support, the pressurized fluid is evacuated from the clamping mechanism at the same time as the piston is being retracted. It is possible that the clamping mechanism unlocks the plunger before the piston has retracted sufficiently. When the clamping mechanism unlocks the plunger, the internal spring can uncompress and extend the plunger. If the piston has not retracted a sufficient distance, the plunger may extend upward with a small force before retracting which may contact and move or dislodge an unclamped work piece, which in turn may cause work piece ejection or location problems for automated equipment handling the work piece.